The present technology relates to the field of additives for fluids such as automatic transmission fluids, traction fluids, fluids for continuously variable transmission fluids (CVTs), dual clutch automatic transmission fluids, farm tractor fluids, engine lubricants industrial gear lubricants, greases, and hydraulic fluids.
In the automatic transmission marketplace, where there is rapid engineering change driven by the desire to reduce weight and increase transmission capacity, there is a desire for automatic transmission fluids that exhibit a high static coefficient of friction for improved clutch holding capacity. Continuously slipping torque converter clutches, for instance, impose exacting friction requirements on automatic transmission fluids (ATFs). The fluid must have a good friction versus sliding speed relationship, or an objectionable phenomenon called shudder will occur in the vehicle. Transmission shudder is a self-excited vibrational state commonly called “stick-slip” or “dynamic frictional vibration” generally occurring in slipping torque converter clutches. The friction characteristics of the fluid and material system, combined with the mechanical design and controls of the transmission, determine the susceptibility of the transmission to shudder. Plotting the measured coefficient of friction (g) versus sliding speed (V), commonly called a μL-V curve, has been shown to correlate to transmission shudder. Both theory and experiments support the region of positive to slightly negative slope of this μL-V curve to correlate to good anti-shudder performance of transmission fluids. A fluid which allows the vehicle to operate without vibration or shudder is said to have good “anti-shudder” performance. The fluid should maintain those characteristics over its service lifetime. The longevity of the anti-shudder performance in the vehicle is commonly referred to as “anti-shudder durability”. The variable speed friction tester (VSFT) measures the coefficient of friction with respect to sliding speed simulating the speeds, loads, and friction materials found in transmission clutches and correlates to the performance found in actual use. The procedures are well documented in the literature; see for example Society of Automotive Engineers publication #941883.
The combined requirements of high static coefficient of friction and durable positive slope are often incompatible with traditional ATF friction modifier technology which is extremely well described in the patent literature. Many of the commonly used friction modifiers result in a low static coefficient of friction and are not durable enough on positive slope to be of sufficient use.
U.S. Pat. No. 4,237,022, Barrer, Dec. 2, 1980, discloses tartarimides and lubricants and fuels containing the same. In an example (IX), an automatic transmission fluid is reported containing the reaction product of tartaric acid with Armeen O (essentially oleylamine).
U.S. Patent Application 2006/0183647, Kocsis et al., Aug. 16, 2006, discloses tartrates, tartrimides, tartramides or combinations thereof useful as additives for lubricants. Various compositions including automatic transmission fluids are said to benefit therefrom. Among the materials disclosed are oleyl tartimide and tridecylpropoxyamine tartrimide. The alkyl groups of the amines may be linear or branched.
U.S. Pat. No. 4,789,493, Horodysky, Dec. 6, 1988, discloses lubricants containing N-alkylalkylenediamine amides. Disclosed is R2—N(R3)—R1—NH—R3 wherein R1 is a C2 to C4 alkylene group, R2 must be a C12 to C30 hydrocarbyl group, and R3 is H, a C1-C3 aliphatic group, or R4—C(═O)—; at least one of the R3s must be R4—C(═O)—. R4 is H or C1-4. An example is Coco-NH—(CH2)3—NH—C(═O)H.
U.S. Pat. No. 3,251,853, Hoke, May 17, 1966, discloses an oil-soluble acylated amine. In examples, reactants can xylyl-stearic acid or heptylphenyl-heptanoic acid, with tetraethylene pentamine or dodecylamine or N-2-aminoethyleoctadecylamine. An example is the condensation product of N-2-aminoethyl)octadecylamine with xylyl-stearic acid.
U.S. Patent publication 2009/0005277, Watts et al., Jan. 1, 2009, discloses lubricating oil compositions said to have excellent friction stability, comprising, among other components, a polyalkylene polyamine-based friction modifier that has been reacted with an acylating agent to convert at least one secondary amine group into an amide.
The disclosed technology, therefore, provides a friction modifier suitable for providing an automatic transmission fluid with a high coefficient of friction or a durable positive slope in a μ-V curve or both.